Cutting tool holder or adaptor

ABSTRACT

This disclosure is directed to a cutting tool holder, wrench or adaptor, as for example, a tap wrench and the like, having a body portion which includes a flexible bellows torque drive which permits limited angular displacement between the body of the holder or adaptor and the center line of the tool bit to maintain alignment between the cutting tool bit and the hole or tap being formed in an associated work piece during a cutting or forming operation. The tool holder further includes a shear safety to prohibit any breakage of the tool bit in the event the applied torque moment exceeds those forces which would otherwise break the tool bit.

United States Patent [191 F abrizio et a1.

[11] 3,753,625 Aug. 21, 1973 CUTTING TOOL HOLDER OR ADAPTOR 22 Filed:July 28,1971

211 Appl.No.: 166,749

[56] References Cited UNITED STATES PATENTS 881,075 3/1908 l-losking408/710 X 903,904 11/1908 Smith 81/177 F 1,776,525 9/1930 Talbot 64/28 R1,870,153 8/1932 Thoman 64/28 R 2,157,996 5/1939 Brownstein 64728 R2,761,298 9/1956 Jarvis 408/710 X 3,301,101 1/1967 McEwen 64/28 R XPrimary ExaminerAndrew R. Juhasz Assistant Examiner-Z. R. BilinskyAttorney-Arthur T. Fattibene 5 7 ABSTRACT This disclosure is directed toa cutting tool holder, wrench or adaptor, as for example, a tap wrenchand the like, having a body portion which includes a flexible bellowstorque drive which permits limited angular displacement between the bodyof the holder or adaptor and the center line of the tool bit to maintainalignment between the cutting tool bit and the hole or tap being formedin an associated work piece during a cutting or forming operation. Thetool holder further includes a shear safety to prohibit any breakage ofthe tool bit in the event the applied torque moment exceeds those forceswhich would otherwise break the tool bit.

17 Claims, 11 Drawing Figures liiiliiln,

Patented Aug. 21, 1973 3,753,625

2 Sheets-Sheet 1 8W La 5552222 3? diam/w ATTORNEY Patented Aug. 21, 19733,753,625

2 Sheets-Sheet 2 F/G. HLJ3A l RALPH 5.54% T R Ql/CHOLAS kjfi o m mz 4 I7% ATTORNEY CUTTING TOOL HOLDER OR ADAPTOR PROBLEM AND PRIOR ART Indrilling, tapping, boring or reaming a hole in a work piece with knowntypes of drilling, tapping, reaming or boring tools, it is imperativethat the requisite amount of torque be applied to the tool bit in anaxial direction in order to maintain hole alignment. In drilling,boring, reaming or tapping a hole in a work piece, it frequently happensthat the application of excessive torque and/or bending moment to thetool would cause the cutting tool, as for example, a tap, to eitheraffect the hole alignment and/or to break within the hole being formedthereby. If breakage occurred, considerable lost time and effort wasrequired to effect removal of the broken bit or tap from the work piece.Not infrequently the work piece in which such tap or tool bit,

broke would be severely damaged during the attempt to effect the removalof the broken tool therefrom.

To overcome this problem of the tool bit breaking in the hole, efiortshave been made to provide such cutting tool bits with a weakened orfrangible area adjacent the upper end of the tool bit so that in theevent excessive torque was applied to the tool bit the bit would breakat a point remote from the hole being formed thereby. By providing forbreakage to occur externally of the hole being formed, removal of thetool from the work piece could thus be facilitated. U. S. Pat. Nos.2,101,347 and 2,740,947 evidence the prior known efforts to provide suchtool bits with a weakened area to alleviate the problem of breaking atool bit or tap in a work piece. However, the teachings of these priorknown efforts do not result in a complete solution to all of theconditions or problems encountered in forming a tap or hole in a workpiece. While the known efforts tended to obviate the problem of breakageof the tool bit from occurring within the hole upon the application ofexcessive torques, the known efforts did not provide a desired solutionto the misalignment problem resulting from the application of excessivetorque and/or bending moment to the tool bit in a nonaxial manner. Thuswith the known tool constructions the application of even a slight forcein a non-axial direction frequently results in a bending moment whichwill adversely affect the trueness or alignment of a hole or bore beingformed. The application of non-axial forces to such tool bits alsogreatly increased the incidence of breakage to occur in the tap or bitand/or at the weakened point thereof. Thus while the known artaccommodated for breakage of the tap or bit to occur at a point remotefrom the hole, there still remained unsolved the problem of maintaininghole alignment in the event excessive torque or bending moment isapplied to the tool bit in a non-axial manner, and/or minimizing theincident of breakage resulting from such bending moments.

i OBJECTS It is therefore an object of this invention to provide a toolholder or adaptor in which effective alignment can be maintained betweenthe cutting tool bit and the hole being formed in the work piece eventhough the torque and/or bending moment is applied in a non-axialdirection.

Another object is to provide an improved cutting tool or holder having aflexible drive coupling for permitting limited angular displacementbetween the tool holder and the center line of the cutting tool or toolbit.

Another object of this invention is to provide a tool holder or adaptorwhich includes a flexible torque drive in conjunction with a shearsafety means for limiting the amount of torque applied to a tool bit toprohibit overstressing the tool bit.

Another object of this invention resides in a tool holder or adaptorhaving a frangible means of predetermined stress which is adapted tofracture when the applied torque moment exceeds a predetermined amount.

Another object of this invention is to provide a tool holder or wrenchto prohibit improper twisting or bending occurring in normalhand turningfrom being transferred to the cutting tool to minimize tool bitbreakage.

Another object of this invention is to provide a cutting tool holder orwrench which enables the user to visibly notice any unusual twisting orbending during a forming or cutting operation.

Another object of this invention is to provide a tool holder or wrenchhaving a flexible torque drive which assures alignment between thecutting tool and the work piece being formed thereby.

BRIEF SUMMARY OF THE INVENTION The foregoing objects and other featuresand advantages are attained by a tool holder, wrench or adaptor having abody defining a tool holding end portion and an opposed handle endportion with a flexible torque drive coupling interposed therebetween.The torque drive coupling comprises a flexible bellows which permitslimited angular displacement between the body of the tool holder orwrench and the center line of the tool bit adapted thereto. Theinvention further contemplates the utilization of a frangible memberhaving a predetermined shear stress which is designed to fracture in theevent the applied torque 'moment applied on the tool holder exceeds apredetermined amount.

In one form of the invention the tool holder may be formed of upper andlower body portions interconnected in driving relationship by thefrangible member designed to fracture when the applied torque momentexceeds a predetermined limit. Provision is also provided forinterchanging variously rated frangible members which are proportionedto the various size tool bits adapted to be accommodated by a givenholder or wrench. This is attained by providing the respective upper andlower body portions with means for receiving any of several differentlysized frangible members so that by the selection of the appropriatefrangible member, the torque imparted to the tool before fracture occursmay be varied according to the size of tool bit being used.

FEATURES A feature of this invention resides in the provision of animproved tool holder or adaptor having a flexible drive coupler whichpermits limited angular displacement between the body and the centerline of the tool bit so as to prevent impropertwisting and/or bendingwhich may occur in turning of the tool body from being transferred tothe tool bit.

Another feature of this invention resides in the provision of a toolholder or adaptor constructed and arranged so as to pennit any excessivetwisting and/or bending to be visibly noted.

Another feature of this invention resides in the provision of a toolholder or adaptor having a flexible torque drive arranged to effectself-alignment of the tool bit to result in greater accuracy in forminga work piece.

Another feature of this invention resides in the provision of afrangible member which will render the tool inoperative in the event theapplied torque is excessive and thereby prohibit the cutting tool itselffrom breaking and/or damaging the work piece.

Another feature of this invention resides in a tool holder or wrenchwhich can be readily adjusted to accommodate any of several varyingloadings to protect any of the variously sized tool bits adapted to beutilized in conjunction therewith.

Other features and advantages will become more readily apparent whenconsidered in view of the dra lugs and specification in which:

FIG. 1 is a side elevation view of a tool holder embodying the presentinvention and having portions thereof broken away.

FIG. 2 is a top plan view of FIG. 1.

FIG. 3 illustrates a modified form of the invention.

FIG. 4 is a plan view taken along lines 4--4 on FIG. 3.

FIG. 5 illustrates a side elevation view of another modified form of theinvention having portions thereof shown in section.

FIG. 6 is a top plan view of the embodiment of FIG. 5.

FIG. 7 is a detailed side elevation view of the frangible memberutilized in the embodiment of FIG. 5.

FIG. 8 is a top plan view of FIG. 7.

FIG. 9 illustrates another modified embodiment of the invention havingportions thereof shown in section.

FIG. 10 is a sectional'view taken along line 10-10 on FIG. 9.

FIG. 11 illustrates a side elevation view of still another modified formof the invention having portions thereof shown in section.

Referring to the drawings there is shown in FIGS. 1 and 2 a cutting toolholder or wrench adapted to detachably receive a cutting tool bit 21 asfor example, a tap, drill, bore, reamer or like cutting tool. It will beunderstood that the tool bit 21 comprises a bit of any conventionalconstruction and consequently the present invention is not directed tothe cutting or tapping tool bit 21, per se, but to a wrench or adaptor20 by which the tool bit may be operated.

The embodiment 20 of FIGS. 1 and 2 comprises a body means 22 having anelongated shank portion 23 which is formed with a plurality oflongitudinally extending spring fingers 23A to define a chuck end forfrictionally gripping the end of a tool bit 21 as for example, a tap orthe like. A chuck collar 24 is suitably threaded to the spring fingers23A of the shank portion 23 for drawing the ends of the spring fingers23A into gripping relationship with the end of the tool bit when thecollar 24 is tightened.

Connected intermediate the body means 22 of the tool holder 20 is aflexible torque drive 25. As shown, the flexible torque drive coupling25 comprises a flexible bellows interposed between the tool end portion24 and the opposite handle end portion 26. As shown, the upper handleend 26 is provided with a transversely extending bore 26A for receivinga handle means in the form of a transversely extending cross arm 27inserted through the bore. The flexible coupling drive 25 is preferablyformed of corrugated sheet material which will permit flexing of thetool body relative to the central longitudinal axis of the tool bit 21and associated shank portion 23.

In operation it will be apparent that the flexible drive coupling 25will permit limited angular deflection of the tool body to occur withouteffecting misalignment between the tool ,bit and the hole being formedor tapped thereby. Consequently as the tool bit 21 is not subjected to abending moment in the event the tool body bends during hand operation,the tool bit 21 is maintained in alignment with the hole being formed.Thus the flexible drive coupling 25 permits angular displacement tooccur between the tool body and the center line of the tool bit withoutresulting in any misalignment to occur between the center line of thetool bit and the hole being formed thereby. The flexible bellowscoupling 25 thus prohibits any improper bending or twisting of the toolbody or wrench which may occur in operation from being transferred tothe cutting tool bit 21. Also the flexible coupling makes visiblyobvious to the user any excessive twisting or bending. The flexiblecoupling 25 also imparts to the tool body a floating action whichinduces a self-aligning feature which enables the tool bit 21 to cutcloser fitting thread or a rearner to cut a closer fitting hole.

FIGS. 3 and 4 illustrate another modified embodiment of the invention.In this form of the invention the tool body 30 is illustrated in theform of an adaptor having a shank portion 31 having formed on one endthereof a socket32 adapted to receive the upper end of a conventionaltool bit 33, as for example, a tap, reamer, drill bit and the like; Theupper end of the tool body 30 is provided with a handle or grippingportion 34 by which the shank may be rotated, e.g. by the chuck end 35of a'conventional wrench.

interposed intermediate the length of the shank portion 31 is a reducedsection 36 which is designed to fracture in the event of any excessivetorque and/or bending moment applied to the tool body during theoperation thereof.

Disposed between the reduced section 36 and the upper end 34 of the toolbody 30 is a flexible drive coupling 38 in the form of abellowsconstruction similar to that described with respect to the embodiment ofFIG. I. In this form of the invention the flexible drive coupling 38 iscooperatively associated with the reduced section 36 of the shank 31 sothat in the event any excessive torque is applied to the tool body, itwill cause the body to fracture at the reduced section, rather than inthe tool bit 33. It will be understood that the shear stress of thereduced section 36 is designed so as to be less than the shear stress ofthe tool bit so that any breakage will occur at 36. Accordingly, thearrangement is such that the tool holder 30 is adapted to fracture at 36before the tool bit breaks or binds in a work piece.

As shown in FIG. 4 the handle or gripping portion 34 extending beyondthe flexible drive coupling 38 is illustrated as being rectangular incross section so as to facilitate the gripping thereof either by hand orby a conventional wrench 35. In operation the tool holder 30 of FIGS. 3and 4 functions in much the same manner as that described withrespect toFIG. 1 with the added provision that a shear means 36 is interposedintermediate the body of the holder to include a frangible sectiondesigned to fracture in the event the applied torque exceeds theshearing or bending stresses of the tool bit 33.

FIGS. 5-8 illustrate another modified form of the invention. In thisform the tool holder 40 comprises an upper body or shank portion 41 anda lower body or shank portion 42. As shown, the lower end 41A of theupper portion 41 is provided with an internal recess 43 which is adaptedto frictionally receive the upper end 42A of the lower shank portion 42.A retaining ring 44 is interposed between the abutting surfaces of theupper and lower shank portion to detachably couple the lower end portion42 to the upper end portion 41.

The lower end portion 42 includes a shank 42B provided with a pluralityof spring fingers 45 to define a chuck end to which a chuck collar 46 isthreaded to define a chuck holding means for detachably securing theupper end of a tool bit 47 thereto.

Connected intermediate the upper shank portion 41 is a flexible drivecoupling in the form of a flexible bellows 48 similar to that describedwith respect to FIGS. 1 and 3. Connected to the upper end of theflexible bellows 40 is a handle means in the form of a transverselyextending cross arm 49 by which the tool holder may be turned.

In this form of the invention the upper end portion 428 of the lowershank member 42 is provided with an internal recess 50 which is adaptedto receive a shear member 51.

Referring to FIGS. 5, 7 and 8 the shear member 51 comprises a memberhaving a reduced section 51A of predetermined shear stress. Connected tothe opposed ends of the shear member 51 is a transversely extendingdriver 52, 53 adapted to be received in complementary slots 52A, 53Aformed in the upper and lower members 41, 42 whereby the shear member 51functions as the drive connector between the upper shank portion 41 andthe lower shank portion 42 in the assembled position as seen in FIG. 5.In the assembled position as seen in FIG. 5, it will be understood thattorque applied to the upper body portion 41 is transmitted to the lowershank portion 42 through flexible torque drive coupler 48 and the shearmember 51. The arrangment is such that the flexible drive coupler 48permits limited angular displacement between the center line of the toolbody and the tool bit without affecting the alignment between tool bit47 and the hole or tap being formed thereby. In the event excessivetorque is applied to the tool body 40, the shear member 51 will fractureat the reduced section 51A before breakage will occur in the tool bit47. Should such excessive torque fracture the shear member 51, anoperator can readily correct the difficulty by effecting separation ofthe upper and lower body portions 41, 42, remove the fractured shearmember, replace the same with a new one; and reassemble the lower shankportion 42 to the upper shank portion 41.

It will be understood that the shear member 51 may be specificallyconstructed to complement a particular tool bit. Thus, the tool holder40 of FIG. 5 may be readily adapted with any of several different shearmembers 51, each having varying breaking points which are rated tocomplement a particular tool bit SIZe.

FIGS. 9 and illustrate another modified embodiment. In this form of theinvention the tool holder 60 comprises an upper body portion 61 and alower body portion 62, each formed with a complementary flange 61A, 62Awhich are adapted to be disposed in abutting relationship in theassembled position thereof.

As seen in FIG. 9 the lower body member 62 is provided with a centerprojection or boss 63 which is adapted to be received within acomplementary recess 64 formed in the lower end of the upper body member61. A retaining ring 65 interconnects the upper and lower body members61, 62 in a readily detachable manner.

Interposed intermediate the upper body portion 61 is a flexible drivecoupler in the form of a bellows 66 constructed similar to thathereinbefore described.

The lower shank portion 62 is provided with a chuck end and collar 67similar to that described in FIGS. 1 and 5.

As best seen in FIG. 10, it will be noted that the complementary flanges61A and 62A of the upper and lower body portions 61 and 62 are providedwith a series of circumscribing spaced openings 68, each opening havinga difi'erent diameter. A shear member 69 in the form of a shear pinhaving a frangible section 69A is inserted through one of the alignedopenings. The shear section 69A of the shear pin 69 is adapted to becoincident with the abutting surfaces of the respective flanges 61A,62A. Accordingly, the arrangement of FIG. 9 is such that whenever anexcessive torque or bending moment is applied to the tool or wrench 60 afracture will occur at the rupture point 69A of the shear member 69. Byproviding a series of varying diameter aligned openings 68 in therespective flanges 61A, 62A, the selection of the appropriate shearmember 69 will adapt tool 60 to a predetermined sized tool bit 70.

FIG. 11 illustrates still another modified form of the invention. Inthis form of the invention the tool holder 71 comprises an upper bodyportion 72 and a lower body portion 73. The lower body portion 73 isprovided with a plurality of spring fingers 73A to define a chuck endfor receiving the end of a tool bit 74 in a manner hereinbeforedescribed with respect to FIGS. 1, 5 and 9; and a chuck collar 75 isthreaded to the spring fingers 73A to effect the expansion orcontraction thereof on the upper end of the tool bit.

Connected to the upper portion 72 is the flexible drive coupling in theform of a bellows 76 similar to that hereinbefore described with theembodiments of FIGS. 1, S and 9. A transversely extending handle 77extends through a bore 78 formed in the upper end or the upper bodyportion. As seen in FIG. 11 the upper and lower body portions '72, 73are provided with complementary male and female components 79 and 80which are interfitted one to the other. As shown, the male and femaleportions 79 and 80 of the upper and lower body portions 72, 73 areprovided with aligned bores 81 extending therethrough adapted to receivea shear member in the form of a shear pin 82 having a reduced section82A designed to fracture at a predetermined shear load. In operation itwill be noted that the tool holder of FIG. 11 will function similar tothe embodiments hereinbefore described. That is, that the shear member82 of FIG. 11 is designed to break or shear before the tap or tool bit74 itself breaks due to any excessive torque, misalignment and/orbending moment applied to the tool body 71. It will be understood thatby controlling the size or stress of reduced sections 82A of the shearmember 82 that the tap holder 71 of FIG. 11 can be adjusted to effect afracture at any predetermined shear load.

From the foregoing description it will be noted that each of thedescribed tool holders is readily adapted to receive conventionallyformed tool bits, and that each holder is constructed to prevent loss ordamage of any finished or semi-finished work pieces due to tool bitbreakage therein. Also the respective tool holders function to preventbreakage and/or loss of the tool bit which frequently may comprise aconsiderable cost item. The respective tool holders are constructed sothat alignment of the tool bit may be maintained in the forming ortapping of a hole even though a bending moment is applied to the toolbody during the turning thereof.

In the embodiments of FIGS. 3, 5, 9 and 11 provisions are also providedfor complementing the flexible drive coupling with shear members adaptedto fracture at a predetermined shear load to preserve the tool bitand/or the work piece being formed thereby in the event of excessivetorque being imparted to the tool holder. The respective tool holdersthus prohibit improper twisting or bending which may occur in operationfrom being transferred to the tool bit, and thereby maintain thealignment of the tool bit and the hole being formed thereby.

While the present invention has been defined with respect to severalembodiments thereof it will be readily appreciated and understood thatvariations and modifications may be made without departing from thespirit or scope of the invention.

What is claimed is:

l. A cutting tool holder adapted to detachably support a cutting toolbit comprising:

a body means,

said body means including a holding means adapted for detachablysupporting a cutting tool bit to said body means,

handle means operatively connected to said body means, and

a flexible coupling means interposed in said body means between saidhandle means and said holding means to permit limited angular deflectionof said body means relative to the center line of said tool bit adaptedto be secured thereto,

and including:

a frangible shear means on said body means having a predetermined shearstress whereby said shear means is adapted to fracture when the appliedtorque on said body means exceeds the predetermined shear stress of saidfrangible means.

2. A cutting tool holder adapted to detachably support a cutting toolbit comprising:

a body means,

said body means including a holding means adapted for detachablysupporting a cutting tool bit to said body means,

handle means operatively connected to said body means. and

a flexible coupling means interposed in said body means between saidhandle means and said holding means to permit limited angular deflectionof said body means relative to the center line of said tool bit adaptedto be secured thereto,

wherein said flexible coupling means includes a bellows torque drive.

3. The invention'as defined in claim 2 wherein said body means includes:

a shank portion,

said tool bit holding means being connected to one end of said shankportion, and

said bellows torque drive being connected to the other end of said shankportion,

and said handle means being connected to said body means above saidbellows torque drive.

4. The invention as defined in claim 3 wherein said holding meansincludes a plurality of spring fingers integrally formed with said shankportion to define an expandible holder for a tool bit,

and a chuck collar threaded to said fingers for detachably securing atool bit between said fingers.

5 A cutting tool holder adapted to detachably support a cutting tool bitcomprising:

a body means,

said body means including a holding means adapted for detachablysupporting a cutting tool bit to said body means,

handle means operatively connected to said body means, and

a flexible coupling means interposed in said body means between saidhandle means and said holding means to permit limited angular deflectionof said body means relative to the center line of said tool bit adaptedto be secured thereto,

wherein said flexible coupling means includes a bellows torque drive,

and a frangible shear means having a predetermined breaking stresswhereby said shear means fractures when the applied torque on saidtorque drive exceeds said breaking stress.

6. The invention as defined in claim 5 wherein said body means includesa shank portion, and

said shear means includes a shear groove circumscribing said shankportion intermediate the ends thereof.

7. The invention as defined in claim 5 wherein said body means includesan upper shank portion and a lower shank portion, and

said shear means being interposed between said upper and lower shankportions.

8. The invention as defined in claim 7 wherein said shear means includesa shear pin having a frangible section interconnecting said upper andlower shank portions.

9. The invention as defined in claim 8 wherein said upper and lowershank portions have complementary laterally extending flanges havingaligned openings therein, and

said shear pin extends through said aligned opening to secure saidflanges together.

10. The invention as defined in claim 9 wherein said flanges include aplurality of circumferentially spaced aligned openings said alignedopenings having progressively increasing diameters for accommodating ashear pin of complementary size whereby the maximum applied torque maybe variedaccordingly.

11. The invention as defined in claim 7 wherein said upper shankportions and lower shank portions have complementary interfittingportions,

means for detachably securing said shank portions together, and

said shear means being interposed between upper and lower shank portionsto connected said portions in driving relationship.

12. The invention as defined in claim 1 1 wherein said upper and lowershank portions define a recess therebetween,

said shear means being disposed within said recess,

said shear means including pin having a frangible section, and

said pin having opposed drive connections, and

said upper and lower shank portions having complementary driveconnections to mate with the drive connections of said pin.

13. A tool holder adaptor comprising:

an adaptor body,

said body having a tool bit holder formed in one end thereof forengaging with the end of a tool bit, and having a shear groovecircumscribing an intermedi ate portion of said body,

a bellows torque drive connected to said body,

and a shank connected to said bellows torque drive extending upwardlythereof,

said shank being adapted to be received in the chuck end of a wrench.

14. A wrench adapted for maintaining the alignment of an associatedcutting tool bit during a cutting operation comprising:

a wrench body having an upper body portion and a lower body portion,

said lower body portion having means for receiving a cutting tool bit,

means for interconnecting said body portions together,

said connecting means including a shear means having a predeterminedfracturing stress,

and a bellows torque drive connected to the upper body portion to permitlimited angular deflection of said upper body portion relative to thelongitudinal axis of said lower body portion and associated tool bit.

15. The invention as defined in claim 14 wherein said upper and lowerbody portions have complementary flanges adapted to be disposed inabutting relationship,

said flanges having aligned openings therein,

said shear means comprising a shear pin extending through said alignedopenings,

said shear pin having a shear groove formed therein, I said shear groovebeing disposed in a plane of the abutting surface of said flanges.

16. The invention as defined in claim 14 wherein said upper and lowerbody portions include complementary interfitting male and female endportions,

said complementary end portions having a transversely extending alignedopening,

and a shear pin extended through said openings for connecting said bodyportions together in driving relationship.

17. The invention as defined in claim 14 wherein said body portionincludes complementary interfitting male and female end portions,

said interconnecting means including a retainer means for detachablycoupling said end portions together,

one of said end portions having a recess formed therein, and

said shear means comprising a shear pin having opposed drive connectors,

and means formed in the respective end portions of said upper and lowerbody portions to engage in driving connection with said driveconnectors. it!

1. A cutting tool holder adapted to detachably support a cutting toolbit comprising: a body means, said body means including a holding meansadapted for detachably supporting a cutting tool bit to said body means,handle means operatively connected to said body means, and a flexiblecoupling means interposed in said body means between said handle meansand said holding means to permit limited angular deflection of said bodymeans relative to the center line of said tool bit adapted to be securedthereto, and including: a frangible shear means on said body meanshaving a predetermined shear stress whereby said shear means is adaptedto fracture when the applied torque on said body means exceeds thepredetermined shear stress of said frangible means.
 2. A cutting toolholder adapted to detachably support a cutting tool bit comprising: abody means, said body means including a holDing means adapted fordetachably supporting a cutting tool bit to said body means, handlemeans operatively connected to said body means, and a flexible couplingmeans interposed in said body means between said handle means and saidholding means to permit limited angular deflection of said body meansrelative to the center line of said tool bit adapted to be securedthereto, wherein said flexible coupling means includes a bellows torquedrive.
 3. The invention as defined in claim 2 wherein said body meansincludes: a shank portion, said tool bit holding means being connectedto one end of said shank portion, and said bellows torque drive beingconnected to the other end of said shank portion, and said handle meansbeing connected to said body means above said bellows torque drive. 4.The invention as defined in claim 3 wherein said holding means includesa plurality of spring fingers integrally formed with said shank portionto define an expandible holder for a tool bit, and a chuck collarthreaded to said fingers for detachably securing a tool bit between saidfingers. 5 A cutting tool holder adapted to detachably support a cuttingtool bit comprising: a body means, said body means including a holdingmeans adapted for detachably supporting a cutting tool bit to said bodymeans, handle means operatively connected to said body means, and aflexible coupling means interposed in said body means between saidhandle means and said holding means to permit limited angular deflectionof said body means relative to the center line of said tool bit adaptedto be secured thereto, wherein said flexible coupling means includes abellows torque drive, and a frangible shear means having a predeterminedbreaking stress whereby said shear means fractures when the appliedtorque on said torque drive exceeds said breaking stress.
 6. Theinvention as defined in claim 5 wherein said body means includes a shankportion, and said shear means includes a shear groove circumscribingsaid shank portion intermediate the ends thereof.
 7. The invention asdefined in claim 5 wherein said body means includes an upper shankportion and a lower shank portion, and said shear means being interposedbetween said upper and lower shank portions.
 8. The invention as definedin claim 7 wherein said shear means includes a shear pin having afrangible section interconnecting said upper and lower shank portions.9. The invention as defined in claim 8 wherein said upper and lowershank portions have complementary laterally extending flanges havingaligned openings therein, and said shear pin extends through saidaligned opening to secure said flanges together.
 10. The invention asdefined in claim 9 wherein said flanges include a plurality ofcircumferentially spaced aligned openings said aligned openings havingprogressively increasing diameters for accommodating a shear pin ofcomplementary size whereby the maximum applied torque may be variedaccordingly.
 11. The invention as defined in claim 7 wherein said uppershank portions and lower shank portions have complementary interfittingportions, means for detachably securing said shank portions together,and said shear means being interposed between upper and lower shankportions to connected said portions in driving relationship.
 12. Theinvention as defined in claim 11 wherein said upper and lower shankportions define a recess therebetween, said shear means being disposedwithin said recess, said shear means including pin having a frangiblesection, and said pin having opposed drive connections, and said upperand lower shank portions having complementary drive connections to matewith the drive connections of said pin.
 13. A tool holder adaptorcomprising: an adaptor body, said body having a tool bit holder formedin one end thereof for engaging with the end of a tool bit, and having ashear groove circUmscribing an intermediate portion of said body, abellows torque drive connected to said body, and a shank connected tosaid bellows torque drive extending upwardly thereof, said shank beingadapted to be received in the chuck end of a wrench.
 14. A wrenchadapted for maintaining the alignment of an associated cutting tool bitduring a cutting operation comprising: a wrench body having an upperbody portion and a lower body portion, said lower body portion havingmeans for receiving a cutting tool bit, means for interconnecting saidbody portions together, said connecting means including a shear meanshaving a predetermined fracturing stress, and a bellows torque driveconnected to the upper body portion to permit limited angular deflectionof said upper body portion relative to the longitudinal axis of saidlower body portion and associated tool bit.
 15. The invention as definedin claim 14 wherein said upper and lower body portions havecomplementary flanges adapted to be disposed in abutting relationship,said flanges having aligned openings therein, said shear meanscomprising a shear pin extending through said aligned openings, saidshear pin having a shear groove formed therein, said shear groove beingdisposed in a plane of the abutting surface of said flanges.
 16. Theinvention as defined in claim 14 wherein said upper and lower bodyportions include complementary interfitting male and female endportions, said complementary end portions having a transverselyextending aligned opening, and a shear pin extended through saidopenings for connecting said body portions together in drivingrelationship.
 17. The invention as defined in claim 14 wherein said bodyportion includes complementary interfitting male and female endportions, said interconnecting means including a retainer means fordetachably coupling said end portions together, one of said end portionshaving a recess formed therein, and said shear means comprising a shearpin having opposed drive connectors, and means formed in the respectiveend portions of said upper and lower body portions to engage in drivingconnection with said drive connectors.